An LED is generally used as a backlight source in conventional LCD devices. A conventional LED drive circuit is shown in FIG. 1. When an ON/OFF signal performs the ON operation and OFF operation at a short interval time, the electrical charges of an output capacitor C1 are not discharged in time when performing OFF operation immediately after the ON operation, so that the charges will be filled into the LED in the next ON operation, and then filled into the normal LED driver. Because the LED drive circuit always has a certain delay time in the ON operation of each time, the LED lights will be enlightened twice, causing blinking.
Besides, when the voltage has a slower rise time, the LED is conducted by low current without reaching the normal voltage. At this moment, the LED will rise slowly, and the eyes will feel the blinking of LED.
To solve the aforementioned problems, there are usually two methods as follows:
1. Accelerating the ON speed so that the eyes cannot judge whether the LED lights are enlightened twice. But accelerating the ON speed will affect the stability of a system loop circuit and the problem of the capacitor electrical charges is not directly solved.
2. Directly adding a discharge resistor at a capacitor end to discharge the capacitor. But directly adding the discharge resistor is equivalent to adding a load, so the circuit power will be consumed all the time and unnecessary consumption will be caused; and once the resistor is damaged, an output end will have a short circuit so that the problem of unsafety will occur.